1. Field of the Invention
The present invention relates to liquid containers comprising an air introduction portion configured to introduce air into a liquid chamber.
2. Description of Related Art
Japanese Laid-Open Patent Publication No. 2005-153285 or its corresponding U.S. Patent Application Publication No. 2005/0134663 A1 describes an ink cartridge for use in an inkjet recording apparatus. The ink cartridge includes an ink supply portion, through which ink contained in an ink chamber is supplied to the inkjet recording apparatus. The ink cartridge further includes an air introduction portion configured to introduce air into the ink chamber. A valve is positioned in the air introduction portion. When the ink cartridge is mounted to the inkjet recording apparatus, the valve breaks a thin film member formed of resin material. Accordingly, the ink chamber is brought into fluid communication with the atmosphere via the air introduction portion. With this structure, the thin film member blocks ink until the ink cartridge is mounted to the inkjet recording apparatus, which reduces ink leakage to the exterior of the ink cartridge via the air introduction portion.
Nevertheless, once the film member breaks when the ink cartridge is mounted to the inkjet recording apparatus, the ink chamber is brought into fluid communication with the atmosphere. Therefore, if the inkjet recording apparatus is moved, ink may leak to the exterior of the ink cartridge via the air introduction portion. For example, if the inkjet recording apparatus is broken and the inkjet recording apparatus is sent for repair to its manufacturer with the ink cartridge mounted on the inkjet recording apparatus, the inkjet recording apparatus may be shaken hard or turned upside down during transportation. This may lead to ink leakage to the exterior of the ink cartridge.
Japanese Laid-Open Patent Publication No. 9-141891 describes an ink cartridge having a gas-permeable film attached to an air introduction portion which brings an ink chamber into fluid communication with the atmosphere. The gas-permeable film allows air to pass therethrough but prevent ink from passing therethrough. In this ink cartridge, the ink chamber always communicates with the atmosphere via the gas-permeable film, and ink leakage to the exterior of the ink cartridge may be reduced even after the ink cartridge is mounted to an inkjet recording apparatus.
As described above, when the gas-permeable film is simply attached to the air introduction portion, ink and the gas-permeable film are placed in a situation in which they may contact constantly. In such situation, for example, when the ink cartridge is transported from its manufacturer to a store which sells the ink cartridge, ink cartridge may be shaken hard enough to make ink contact with the gas-permeable film during transportation. Contact between ink and the gas-permeable film may cause ink meniscuses to be formed in pores in the gas-permeable film, which may prevent air from being introduced into the ink chamber. Ink and the gas-permeable film may contact before the ink cartridge is mounted to the inkjet recording apparatus. When such ink cartridge is mounted to the inkjet recording apparatus, and ink in the ink chamber is continued to be supplied to the inkjet recording apparatus, the pressure ink the ink chamber decreases because air cannot be introduced into the ink chamber. This pressure drop in the ink chamber may cause the inkjet recording apparatus to fail to perform printing properly.
Therefore, even when the gas-permeable film is used in the air introduction portion, it may be preferred to reduce opportunities that ink and the gas-permeable film contact with each other. In particular, before the ink cartridge is mounted to the inkjet recording apparatus, it may be desired to avoid contact between ink and the gas-permeable film.
Moreover, to reduce an installation space for the inkjet recording apparatus, demands on reduction in physical size of the inkjet recording apparatus are increasing recently. Accordingly, reduction in physical size of the ink cartridge also may be desired.